So many beta patch threads...
... anyway. Thought I'd drop the res I was playing in (1920X1200) to 1680x1050, and turned off AA. Was an improved FPS as expected but oh my, low level flying around the country-side was a lot worse in respect of stutters. :s
Naturally, went back to original settings.
There's also somewhere I'd like others to try:
Near the sea-side town, there is an industrial estate, just north of that is a long rail bridge, as soon as this came into view my FPS dived and a slide-show ensued. Really bad. So I flew out to sea, but it didn't improve much. Bizarre.
Would be nice if others could check to see if they get the same problem.